* Separatist rebels said Nov. 29 they were ending ceasefire
* Plume of black smoke hangs over Kidal
* Some al Qaeda-linked fighters still in northern Mali
By Adama Diarra and Tiemoko Dialla
BAMAKO, Dec 14 (Reuters) - A car bomb killed two U.N. Senegalese peacekeepers and destroyed the only operating bank in the northern Malian town of Kidal on Saturday, one day before a second round of parliamentary elections.
There was no immediate claim of responsibility for the attack at 0645 local time (0645 GMT) on the Malian Solidarity Bank, which was being guarded Mali's army and the U.N. peacekeeping mission known as MINUSMA.
"A car bomb targetted MINUSMA forces and the Malian army who were guarding the building of the Malian Solidarity Bank in the centre of Kidal," said a statement by MINUSMA, which condemned the attack.
"The explosion caused the death of two Senegalese blue helmets and also caused a number of serious injuries among the ranks of the Malian national guard and MINUSMA," the statement said.
Some fighters linked to al Qaeda are still holding out in the north nearly a year after the start of a French offensive aiming to drive them from the desert region they occupied for most of 2012 after hijacking a Tuareg separatist rebellion.
A military source said MINUSMA troops were guarding the outside of the bank while the Malians protected the inside.
"A vehicle in front of the bank is in flames after the explosion. There is a huge amount of black smoke in the sky hanging over the town," resident Ibrahim Maïga said. Another resident, Youssouf Touré, said the bank was reduced to rubble.
It was not clear whether the bank was open for business at the time.
Mali's three main political parties secured just 16 seats out of 147 available in the first round of a parliamentary election on Nov. 24. A second round was scheduled for Sunday in constituencies where there was no clear winner.
Few reports of violence surrounded the November poll, which was held to complete a transition to democracy after a coup last year led to an Islamist takeover of the north.
The rebels, who demand an independent homeland they call Azawad, ended a five-month ceasefire on Nov. 29, a day after Malian troops clashed with stone-throwing protesters who blocked a visit by the prime minister to Kidal.
The French-led offensive scattered Islamists across Mali and into neighbouring countries but the groups have stepped up operations in recent months, attacking U.N. peacekeepers and killing two French journalists in Kidal last month.
The Tuaregs seized control of Kidal after the French offensive had driven Islamists out of the town, leading to tensions with the government in Bamako.
Under a June peace pact that allowed the army to return to Kidal, rebels are still inside the town but are required to return to their barracks under U.N. supervision, stop carrying arms in public and dismantle all roadblocks.